Process and apparatus for surfacing sheet glass



Sept. 26, 1933. "r. c. MCKINLEY PROCESS AND APPARATUS FOR SURFACING SHEET GLASS Filed July 13, 1931 INVENTOR Thomas C.Mc K mien 1 ATTORN EY Patented Sept. 26,1933

PROCESS AND APPARATUS 'Foa SURFAC- mo SHEET GLASS Application July 13, 1931. Serial No. 550,389

9 Claims.

The present invention relates to an improved process and apparatus for surfacing sheet glass.

In the surfacing of sheet glass according to the continuous system, a plurality of sheets of glass 7 to be surfaced are mounted upon a'series or train of cars or tables and passed in a definite substantially horizontal path first beneath a series of grinding runners and then beneath a series of polishing runners to surface one side of the sheets, after which the said sheets are turned over upon the tables and again passed beneath the same or a second series of grinding and polishing runners to surface the second side.

The grinding runners employed in the continuous system referred to above are relatively very heavy, being ordinarily in the form of substantially solid discs constructed of cast iron or the like. These runners are also usually carried at the lower ends of vertically disposed drive spindles L in such a manner that they are permitted a limited amount of universal rocking and vertical bodily movement.

The principal aim and object of this invention resides in the provision of a novel process and apparatus for facilitating and improving the grinding of the glass sheets and in lessening the danger of breakage of the glass such as is sometimes occasioned by the rocking of the grinding runners thereon." I l j Other objects andadvantages of the invention will become more apparent during the course of the following description when taken in connection with the accompanying drawing. In the drawing forming a part of this application and wherein like numerals are employed to designate like par-ts throughout the same,

Fig. 1 is a diagrammatic plan view of one form of apparatus-which may be employed for carrying out the present invention,

Fig. 2 is an end elevation of one of the glass carrying tables, showing agrinding runner positioned thereabove,

Fig. 3 is a transverse section taken substantially on line 33 of Fig. 1, and

' Fig. 4 is a plan view of an alternative arrangement.

Referring now to the drawing, and especially with reference first to Figs. 1 to 3, there is disclosed a plurality of cars or tables 5 mounted upon wheels 6 and being movable along'the track 7 in a definite substantially horizontal path by any suitable propelling means which may include, for example, a drive pinion (not, shown) meshing with rack bars 8 carried upon the bottoms of the said tables. These tables 5 are adapted to sup mounted at the lower end of a vertical drive port a series of glass sheets 9 to be surfaced, the said sheets being preferably secured upon the tops thereof by embedding them within a layer of plaster of Paris or the like 10. The tables 5 are adapted to carry the glass sheets 9 first beneath 0 a series of grinding runners 11 and thence beneath a series of polishing runners (not shown) to grind and polish the upper surfaces of the sheets, after which the said sheets are turned over upon the tables and again passed beneath the same or a second series of grinding and polishing runners to surface the second side.

The grinding runners 11 are in the form of single substantially solid discs carried at the lower ends of vertical drive spindles 12 and each having a series of spaced grinding lugs or projections 13 formed upon the under surface thereof. The grinding runners are also preferably of a diameter relatively greater than the width of the glass carrying tables and, in addition, are preferably connected to the drive spindles 12 in such a manner that they are permitted a limited amount of universal rocking and vertical bodily movement.

In the past, the sheets of glass 9 constituting the plate glass blanks and having relatively fiat and substantially parallel surfaces were secured upon the tables 5 and passed directly beneath and in contact with the relatively large heavy grinding runners 11. However, it has been found that relatively better results can be obtained in the grinding operation if the surface of the, plate glass blank is initially relatively concave at the beginning of the grinding operation or, in other Words, if the central portion of the sheet is slight- 1y. recessed and therefore thinner at this point than at the opposite sides thereof. With such an arrangement, the grinding runners 11 seat themselves better upon the glass during the grinding thereof, as a result of which the tendency of the runners to rock or tip upon the sheets is materially lessened and, as a consequence, breakage of the glass from this cause is reduced to a minimum.

Therefore, in accordance with the present invention, there is provided in advance of the main grinding runners 11, which act upon the glass sheets throughout their entire width, a relatively smaller and lighter grinding runner 14 also spindle 15. This auxiliary runner 14 is of a smaller diameter than the main runners 11 and is disposed above the central portion of the glass sheets. In other words, it does not extend the entire width of the tables 5 but, on the other hand, effects a grinding of the central portion only of the sheet so as to grind this portion slight- 1y thinner than the opposite side portions thereof. As shown in Fig. 3, the grinding action of the auxiliary runner 14 serves to form a recess or depression 16 at the central portion of the glass sheet so that the said sheet, when initially subjected to the action of the runners 11, will have a slightly concaved upper surface. As the glass grinding runners 11, this recess or depression 16 will be ground out or removed so that, after the completion of the grinding and'polishing operation, the said surface .will be plane or fiat. After the upper surfaces of the glass sheets have been both ground and polished, the saidsheets are turned over upon the side treated in the same manner. grinding the central portion only of the sheet to form the depression or recess 16 therein, the heavy grinding runners 11 will seat themselves better upon the glass during the grinding thereof so that there is less rocking of said runners and consequently less breakage of the glass.

In Fig. 4 is shown a slightly modified arrangement which differs from that previously described in that, in lieu of employing a single relatively small grinding runner 14 in advance of the main runners 11, there are provided the three auxiliary grinding runners 17, 18 and 19 which gradually increase respectively in diameter. Thus, the glass sheets are subjected first to the grinding action of the smallest runner 17 and thence to the runners 18 and 19 before being acted upon by the main heavy runners 11.

It is to be understood that the form of the invention herewith shown and described is to be taken as thepreferred embodiment of the same, and that various changes in the shape, size and arrangementof parts may-be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.

I claim:

1. In apparatus for surfacing sheet glass, means for supporting and conveying the sheets in a definite predetermined path, grinding means acting upon theupper surfaces of the sheets throughout their entire width, and auxiliary grinding means in advance of-the first mentioned grinding means and acting upon the upper surfaces of the said sheets across only a portion grinding means of thewidth thereof.

2. In apparatus for surfacing sheet glass,

7 means for supporting and conveying'the sheets in a definite predeterminedpath, grinding means acting upon the upper surfaces of the sheets throughout their entire width, and auxiliary grinding means in advance of the first mentioned and actingupon the central portions only of the sa d sheets to form recesses in the upper surfaces thereof.

sheets are then carried beneath the main tables and the second. By initially- 3. In apparatus for surfacing sheet glass, means for supporting and conveying the sheets in a definite predetermined path, rotatable grinding members acting upon the upper surfaces of the sheets throughout their entire width and an auxiliary rotatable grinding member in advance of the first mentioned grinding members and acting upon the upper surfaces of the said sheets across only a portion of the width thereof.

4; In apparatus for surfacing sheet glass, means for supporting and conveying the sheets in a definite predetermined path, rotatable grinding members'acting upon the upper surfaces of the sheets throughout their entire Width, and an auxiliaryrotatable grinding member in advance ofthe first mentioned grinding members and acting upon the central portions only of the said sheets to'form recesses in the upper surfaces thereof.

5. In apparatus for surfacing sheet glass, means for supporting and conveying the sheetsina definite predetermined path, grinding means acting upon the upper surfaces of the sheets and extending the entire width thereof, and auxiliary grinding means in grinding means and also acting upon the upper surfaces ofthe said sheetsbuti extending across only a portion of the. width thereof.

6. In apparatus for surfacing-sheet glass,'means for supporting and conveying definite predetermined path, grindingumeans acting upon the upper surfaces of the sheets and extending the entire width thereofand auxiliary grinding means in advance of the first mentioned advance of .the first mentioned the sheets in a grinding means and arranged above the centralv portions only of the said sheets.

' '7. In apparatus for. surfacing sheet glass,means for supporting and conveying the sheets in a definite predetermined path, rotatable grinding membersacting upon the upper surfaces of the 1 sheets and extending the entire width thereof, and a rotatable auxiliary grinding member in advance of the first. mentioned-grinding members and also acting, upon the upper: surfaces of the said sheets but extending across only av portion' of the width thereof.

8. In apparatus for. surfacing sheet glass; means for supporting and. conveyingthe sheets ina definite predetermined path, rotatable grinding members acting upon sheetsand extending the entire width thereof; and arotatableauxiliary grinding member in advance of the firstmentioned grinding members and arranged above. the central'portions', only of the said sheets.

9. The processof surfacing'sheetrglass;which consists in passing the sheet. to be treatedin a definite predeterminedpath, in grinding thesaid sheet initially at the center thereof',,and"in:th en grinding the same across' its entire .width. 1

THOMAS C. McKINLEY.- 

